Photographic developer solutions of high sulfite content and ph

ABSTRACT

SILVER SALT IMAGES ARE RAPIDLY DEVELOPED IN THE PRESENCE OF A COLOR FORMER CAPABLE OF FORMING A QUINONEIMINE OR AZOMETHINE DYE, AND AN AROMATIC PRIMARY AMINE COLOR DEVELOPING AGENT AT A PH OF 12.5-15.0, AND AN ALKALI METAL SULFITE CONCENTRATION OF 0.15 M TO 0.75 M. THE PROCESS AND DEVELOPER SOLUTIONS ARE USEFUL IN FORMING MULTICOLOR IMAGES IN COLOR FILMS AND IN FORMING COLORED RADIOGRAPHIC IMAGES.

Uited Stas ABSTRACT OF THE DISCLOSURE .Silver salt images are rapidly developed in the presence of a color former capable of forming a quinoneimine or azomethine dye, and an aromatic primary amine color atent developing agent at a pH of 12.5-15 .0, and an alkali metal sulfite concentration of 0.15 M to 0.75 M. The process and developer solutions are useful in forming multicolor images in color films and in forming colored radiographic images.

BACKGROUND OF THE INVENTION This invention relates to color photography. More particularly it relates to processing solutions and techniques for producing colored photographic elements. Still more particularly, this invention relates to rapid-access radiographic processes which are also economical and suitable for use in automatic or continuous processing machines.

Differentiation of image areas is difiicult in black and white radiographs due to limited change in density and intensity. It is well known in the art to develop radiographs in the presence of color couplers to form colored images with greater differentiation; however, prior art processes have been limited by (1) developer instability due to low sulfite content, (2) the slow rate of coupling development, (3) color developer incompatibility with black and white products, and (4) developer toxicity.

The prior art shows that although high sulfite content in the developing solutions is desirable for increased stability, the dye density is decreased and a heavier coating weight is required to compensate for the loss in dye coupling which is a result of the high sulfite concentration. These prior developers have a sulfite concentration less than 0.1 M and a pH not over 12. It is also common in the prior art to employ two different radiographic films, one for low contrast plus high latitude and another for high contrast.

The processing baths of this invention have a high sulfite concentration and are therefore stable; yet, surprisingly, there is no accompanying loss in developed density. The developers have a sulfite concentration similar to normal black and white developers, e.g., 40 grns. alkali sulfite per liter, but dissimilar to most color developers and are therefore more stable than most color developers.

The addition of black and white developing agents to color developing solutions to increase the rate of color development is well known in the art. It is known that black and white developing agents activate color developers.

With modern-day automatic processing of radiographs, it is desirable to have a developer formula suitable for both conventional black and white X-ray film and coupling X-ray film so that both types of film may be fed through the machine with only relatively minor adjustments. There is also great interest today for improvement in photographic speed, resolution and access time (the time within which the image is made available for inspection and use).

It is common practice, today, to process radiographs in 90 seconds, dry-to-dry, in automatic machines. To keep up with this progress, color development should be completed in about 20 seconds or less and the solution should be stable to minimize maintenance at the high development temperatures normally employed. Though it is known that increasing amounts of alkali, e.g., NaOH, usually cause steady increase in development rate, the sudden increase in development rate and insensitivity to sulfite ion concentration, observed at pH=12.5, is surprising and indicates a change in the development mechanism.

The developer solutions and processes of this invention are useful with a low silver halide coating weights in machine processing, and permit very rapid access and improved diagnosis of radiographs via improved latitude and variable contrast, replacing two prior art black and white radiographs and only one colored radiograph. The developing baths are also stable over a long period of use.

SUMMARY OF THE INVENTION It is an object of this invention to provide rapid and economical means for processing photographic film elements. Another object is to provide such a means which is useful in automatic processing machines and with both black and white and color film. Still another object is to provide stable photographic developing solutions which allow for the production of radiographic images that have improved contrast and rendition of detail.

The objects of this invention are accomplished by developing an exposed film element in the presence of a color former capable of forming a quinoneimine or azomethine dye, in solutions having pH 12.5 to 15.0, a sulfite concentration of 0.15 M to 0.75 M, and a color developing agent of aromatic primary amine type. Low coating weight silver halide layers can be developed adequately with the solutions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment of this invention, an exposed silver halide emulsion, prepared by the procedure used in Example I of Firestine and Umberger, U.S.P. 3,163,625, Dec. 29, 1964, containing a polyanion naphthol color-former of the polyvinyl ether type is developed in a solution that is 0.2 M in alkali sulfite, has a pH: 13, and contains the color developing agent p-aminophenol and a non-color coupling developing initiator, such as a 3-pyrazolidone, e.g., l-phenyl-3-pyrazolidone.

Useful color couplers contain chemical groups capable of coupling with oxidation products of aromatic primary amine developing agents, e.g., p-phenylenediamine or paminophenol, formed during the development of silver salt images, to form a quinoneimine or azomethine dye. These color formers are also capable of forming in certain instances an azo dye image. The nuclei have the structure which may be represented by the formula where =1 is =(l3H, :OOI, =(ilBr, =CIJSOJM, or =1? which is a general structure of the color-coupling nucleus in an enol form where M is H, metal, or amine cation.

These nuclei are found in the reactive methylene dye intermediates and in aromatic hydroxyl compounds. These groups occur in phenols, naphthols, acylacetamides, cyanoacetyls, beta-ketoesters, pyrazolones, homophthalimides, coumaranones, indoxyls, thioindoxyls, and indazolones.

Color couplers which satisfy the above requirements are the migratory type, e.g., l-naphthol or 2,4-dichlorol-naphthol, the soap-type, e.g., N-octadecyl-1-hydroxy-4- sulfo-2-naphthamide, the oleophilic or oil-dispersible type, e.g., N-octadecyl-1-hydroxy-2-naphthamide, and the poly- 3 meric type. The polymeric type may be of the Watersoluble and gelatin-compatible type of US. 3,163,625 or the oil-soluble dispersible type of US. Ser. No. 419,227 filed May 29, 1961; preferably they are prepared by addition polymerization of ethylenically unsaturated monomers with attached coupling function, e.g.,

as described in US. 3,163,625.

For improved physical properties and kink-resistance of the emulsion or antiabrasion layers, a coupling latex from a dispersed copolymer of the above monomer with an oleophilic comonomer, e.g., ethyl acrylate or diethyl maleate is preferred.

Though all of the above types of couplers are anticipated by this invention, it was found that the phenolic couplers and preferably the naphthols are most rapid in coupling and especially those Without a substituent in the coupling position.

The color couplers and aromatic primary amine color developing agent may be incorporated directly into the emulsion layer or the antiabrasion layer during the manufacture of the light-sensitive material or may be dissolved in the color developing solution or a monobath with fixer so that it diffuses into the emulsion layer during the color development process. The developing solution or element may contain a single coupler or a combination of couplers and may contain a single color developing agent or a combination, e.g., a p-phenylenediamine plus a p-arninophenol having an unsubstituted-N11 group.

The processing solutions or elements of this invention contain primary aromatic amine color developing agents, the oxidation products of which that are formed during the development of exposed silver halides combine with the color coupler to impart extra image density to the silver image. Useful such color developing agents include those listed in column 8 of Jennings US Pat. 2,551,134, May 1, 1951. These agents are usually used in the form of their addition salts, e.g., HCl or H 80 or acetic acid salts.

It is often desirable to have a low concentration of certain development initiators present in the element or in the processing bath, to increase the rate of color development. Although 1-phenyl-3-pyrazolidone and related B-pyrazolidones and metol and certain other p-arninophenol derivatives are preferred, any compound having the following generic structure is suitable for the purpose of the invention where Y=C or N; R =H, lower alkyl or bifunctional radicals closing a ring wth R or with the bond X; R =alkyl, aryl or bifunctional radical closing a ring with R X=a bond closing a ring with Y or R n is preferably l or 2.

When the color coupler or the color developer is omitted from the processing of the exposed silver halide emulsion, a relatively Weak image results. Development of the exposed film element in the presence of a color coupler, a color developing agent, and a development initiator results in high contrast with large increases in image density. This superadditive effect produced by the three ingredients permits a decrease in the silver halide coating weight.

The pH of the developing solution should be between 12.5-15 to permit rapid access and a high sulfite concen tration without an accompanying loss in image density and contrast. At such a high pH, the sulfite ion concentration can be raised to 0.2 M or higher resulting in a color processing bath approaching the stability of conventional black and white developing solutions.

The film elements which may be treated by the processing baths and procedures of this invention may be overcoated with an aldehyde-containing abrasion coating containing gelatin mixed with polymeric coupler for cross-linking the gelatin and the coupler. The color coupler and/or the color developing agent may be incorporated into the antiabrasion layer.

The invention will be further illustrated by the following specific examples.

Example I Polyethylene terephthalate photographic film base of thickness .007 inch (F. P. Alles, US. 2,779,684) was coated on both sides with a conventional silver halide X- ray emulsion consisting of silver bromide grains of about 12 microns average diameter and 1 mole percent iodide at a dry coating weight of about 45 mg./dm. of silver bromide. Gelatin, saponin and a polymer latex made by copolymerizing ethyl acrylate with the coupling monomer (disclosed in assignees copending application of Umberger, Ser. No. 419,227, died Dec. 17, 1964) were also present in the emulsion layer. There was 67 grams of coupler polymer per mole of silver bromide.

The dried emulsion layers were overcoated with a dilute solution of gelatin containing hardeners chrome alum and formaldehyde and wetting agents saponin and dioctyl sodium sulfosuccinate.

The coated polyester film base was then exposed to actinic radiation through a negative (2l /2 step Graphic Arts Technical Foundation exposure Wedge) on a Universal 1B Intensity-Scale 500W incandescent light sensitometer, and two samples of the exposed film element were developed in the following developer baths:

Developer A:

Water-800 ml. Sodium sulfite (anhy.)2.0 g. p-Phenylenediamine-l 1.0 g. Potassium bromide8.0 g. Benzotriazole-O. 15' g.

l-phenyl-3-pyrazolidone0.l0 g. Sodium carbonate (anhy.)40.0 g. Water-sodium hydroxide to 1 liter and final pH of 12.0.

Developer B:

Water800 ml. Sodium sulfite (anhy.)40.0 g. p-Phenylenediamine-1 1.0 g. Potassium bromide8.0 g. Benzotriazole0.15 g. 1-phenyl-3-pyrazolidone0.10 g. 1 Sodium carbonate (anhy.)40.0 g. Water-sodium hydroxide to 1 liter and final pH of 12.0.

Development in Solution A, containing the low sulfite concentration, at F. required 45 sec. and produced a blue-black image of visual density 2.75. Development in Solution B, with high sulfite, produced an image of visual density 2.24 after 45 sec. development.

Developer Solutions A and B were again prepared except that in this instance the final pH of the two solutions was adjusted to 13.0 with sodium hydroxide. Two samples of exposed film element were then developed and the two developer baths compared.

Development in bath A, with low sulfite concentration and pH of 13.0, at 90 -F. required 15 sec. and gave an image of visual density 2.8. Development in bath B, with high sulfite and pH 13.0, at 90 F. required sec. and surprisingly produced a visual image density of 2.9, again blue-black in color.

After development of the sensitometric strip, the film was fixed in the following solution: 5

Water-600 cc.

Sodium thiosulfate (anhy.)153 g. Sodium boratel8 g.

Sodium sulfite (anhy.)-l5 g. Glacial acetic acid-12 cc. Potassium alumg.

Water to 1 liter.

The final product was washed in cold water and dried. After use, the high sulfite developer was less colored, e.g., by oxidation products, than the low sulfite developer.

When a non-color coupling developer was used on this film, e.g., a metol-hydroquinone X-ray developer, a coating weight of silver bromide about twice as great as that used above was required to obtain the same image density.

When Example I was repeated at pH 13 but in the absence of 1-phenyl-3-pyrazolidone, somewhat longer development times were required but the same result was obtained, viz., the high sulfite solution developed equal or greater image density than the low sulfite solution.

Example 11 A color positive print was prepared by exposing commercially available Agfaeolor MCN III paper, manufactured by Agfa Gevaert, to actinic radiation using the procedures of Example I. The color positive comprised three layers of silver halide emulsion on a white-pigmented, baryta-treated support. The emulsion layer nearest the support contained a cyan coupler similar to OjCONHCML- S OgH The middle layer contained a magenta coupler like SO H The final coating of silver halide emulsion contained a yellow coupler like (I) O OH JOOH The final pH was adjusted to 13.0 with a dilute aqueous solution of sodium hydroxide. Developing time was 20 sec. at 80 F.

The color print was then treated in the following two solutions:

Stop-Fix: v G. Sodium thiosulfate (anhy.) 100 Sodium bisulfite 15 Sodium sulfite 10 Water to 1 liter.

Bleach-fix: G. Ethylenediaminetetraacetic acid, sodium salt 47 Ferric chloride (FeCI -6H O) 25 Sodium sulfite 10 Ammonium thiosulfate 200 Thiourea 10 Potassium phosphate (KH PO 20 Potassium phosphate (K HPO 10 Water to 1 liter.

Development of the color positive print in the high sulfite developer appeared to prevent surface stain and image mottle and dye bleeding relative to a low sulfite developer. When exposed to masked or unmasked color negative in an enlarger, the positive color prints obtained with the rapid access, stable coupling developers compared favorably in speed and contrast to color prints exposed similarly with more conventional slower processing at lower pH and sulfite concentration. The high pH, high sulfite developer was less colored by aerial oxidation than coupling developer containing the usual amount of sulfite, e.g., 5 gms./l.

Example III The element of Example I was exposed as described in that example and processed in Developer C.

Water to 1 liter.

When adjusted to pH 11 with sodium hydroxide, Developer C was weak-acting and formed images of silver, only, i.e., no dye formation occurred. Increasing the pH to 12 with sodium hydroxide still did not yield satisfactory dye coupling. Addition of 22 gms. of sodium hydroxide to the developer solution, to a pH of 12.5, resulted in dye image as well as metallic silver image, but practical radiographic tests showed some dye image bleeding. At pH 12.5 the bleeding decreased.

Surprisingly, the developed image from p-aminophenol was reddish or magenta in color. At first it was thought that bluish-black images of Example I, with p-phenylenediarnine, were preferable due to the relation to bluetinted base normally used for medical X-ray film; but subsequent viewing of the red-black images of Example 111 with green-emitting fluorescent tubes as illuminant indicated improved image contrast and visibility. This appeared as a result of the high visual opacity of red-black images to the receptors in the human eye which has a maximum sensitivity at 530-550 me. Also, the green-emitting phosphors of mercury-vapor fluorescent tubes are almost twice as visually bright as the usual daylight phosphors due to the efiiciency of the green phosphors, ZnSiOgzMn.

Developer C was also advantageous in its low toxicity and dermatitis inactivity. It also yielded a developer compatible with black and white X-ray films. Black and white medical X-ray films were found to process to equal contrast, speed and density for similar times in Developer C e.g., two minutes at F., as in standard black and white developer, e.g., like Developer C but vw'th 20 gms. of hydroquinone replacing the 30 gms. of p-aminophenol hydrochloride.

The developing solutions of this invention are useful in the processing of both black and white and color film. Film elements which are suitable for development by the processing baths herein described include radiographic film, color positive, color negative, and color reversal film.

With some adjustment, the processing baths may be used for developing both black and white and color film.

The novelty of the present invention is that a color coupler and a high concentration of sulfite ions may be used in the processing of photographic film without a decrease in the efiiciency of the system. Other advantages include the following: (1) developing solution is suitable for both black and White and color rapid-access processing and therefore may be incorporated into an automated processing system, (2) silver is conserved, thereby reducing the silver halide coating weight requirements, (3) developer life is lengthened as a result of high sulfite concentration, (4) high exposure sensitivity, (5) high contrast images, (6) improved latitude and variable contrast, and (7) high sulfite concentration helps to prevent interlayer color contamination caused by migration of color-couplers and oxidized developer molecules and yields processed film free from haze due to prevention of excessive emulsion swelling in alkaline developers.

Suitable sulfites include sodium, potassium, and ammonium sulfites, but the preferred sulfite that is used in the processes and solutions of this invention is potassium sulfite.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An aqueous developer solution for forming dye images upon color coupling development of an exposed photographic silver halide layer in the presence of a color former capable of forming a quinoneimine or azomethine dye and a primary aromatic amine color developing agent, characterized in that said solution has a pH of at least 12.5 and an alkali metal sulfite concentration of at least 0.15 M.

2. An aqueous developer solution according to claim 1, wherein the pH is 12.5 to 15.0 and the alkali metal sulfite concentration is 0.15 M to 0.75 M.

3. A developer solution according to claim 1 containing a color former capable of forming a quinoneimine or azomethine dye upon development of silver halide images.

4. A developer solution according to claim 1 containing a 3-pyrazolidone developing agent.

5. The process which comprises developing an exposed photographic silver halide emulsion layer in the presence of a color former capable of forming a quinoneamine or azomethine dye and a primary aromatic amine color developing agent, characterized in that said solution has a pH of at least 12.5 and an alkali metal sulfite concentration of at least 0.15 M.

6. A process according to claim 4, wherein said layer is a radiographically-exposed layer.

7. A process according to claim 4, wherein said color former is a naphthol.

8. An aqueous developer solution according to claim 1 wherein the pH is at least 13.0.

References Cited UNITED STATES PATENTS 2,301,387 11/1942 Evans et al. 9666.4 2,772,973 12/1956 Britain 9656 3,211,552 10/1965 Chu et al. 9656 3,342,599 9/1967 Reeves 9666.4

OTHER REFERENCES Mason: Photographic Processing Chemistry, p. 223, The Focal Press, New York (1966).

J. TRAVIS BROWN, Primary Examiner US. Cl. X.R. 

